\begin{table}[htbp]\centering
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\caption{Effect of MPD on the logarithm of net prices \label{tab1}}
\begin{tabular}{l*{4}{c}}
\toprule
                    &\multicolumn{1}{c}{(1) E5}&\multicolumn{1}{c}{(2) Diesel}&\multicolumn{1}{c}{(3) E5 (oil price)}&\multicolumn{1}{c}{(4) Diesel (oil price)}\\
\midrule
treated             &      -0.033\sym{***}&      -0.018\sym{***}&      -0.030\sym{***}&      -0.015\sym{***}\\
                    &     (0.003)         &     (0.003)         &     (0.006)         &     (0.005)         \\
\midrule
Observations        &        1258         &        1258         &        1258         &        1258         \\
Adjusted \(R^{2}\)  &       0.868         &       0.836         &       0.879         &       0.860         \\
\bottomrule
\multicolumn{5}{l}{\footnotesize Standard errors in parentheses}\\
\multicolumn{5}{l}{\footnotesize \sym{*} \(p<0.10\), \sym{**} \(p<0.05\), \sym{***} \(p<0.01\)}\\
\end{tabular}
\end{table}
